This invention relates to an ink jet printhead. More particularly, the invention relates to an Actuator Anchor.
Most ink jet printheads of the type manufactured using micro-electro mechanical systems (MEMS) technology have been proposed in a construction using nozzle chambers formed in MEMS layers on the top of a substrate with nozzle chambers formed in the layers. Each chamber is provided with a movable paddle actuated by some form of actuator to force ink in a drop through the nozzle associated with the chamber upon receipt of an electrical signal to the actuator. Such a construction is typified by the disclosure in my International Patent Application PCT/AU99/00894.
The present invention stems from the realisation that there are advantages to be gained by dispensing with the paddles and causing ink drops to be forced from the nozzle by decreasing the size of the nozzle chamber. It has been realised that this can be achieved by causing the actuator to move the nozzle itself downwardly in the chamber thus dispensing with the paddle, simplifying construction and providing an environment which is less prone to the leakage of ink from the nozzle chamber.
According to the invention there is provided an ink jet printhead including:
a plurality of nozzles mounted to a rigid substrate, each of the nozzles being adapted to eject drops of ink toward a surface to be printed;
each of the nozzles also having a bend actuator and an apertured roof portion, the bend actuator adapted for anchorage to the rigid substrate and connection to the apertured roof portion such that in use the actuator moves the roof portion away from the surface to be printed, in order to eject the ink; wherein,
the displacement of all points along the operative section of the bend actuator during its movement from a de-activated to an activated state, constantly increases from zero displacement at the point of anchorage to the rigid substrate, to maximum displacement at the point of connection to the apertured roof portion.
Preferably, each of the nozzles further includes an associated nozzle chamber adapted to be supplied with ink via at least one conduit in the underlying substrate.
Preferably, the roof portion has a sidewall depending from its periphery to telescopically engage a peripheral sidewall extending from an opposing floor portion to define the nozzle chamber.
Preferably, the bend actuator is anchored on the substrate at a proximal end as a cantilever beam, arranged to support the roof portion of the nozzle chamber at a distal end thereof, and wherein the bend actuator comprises at least one Joule heated cantilever in parallel with a non-heated cantilever joined together at the distal end.
Preferably, the bend actuator is mounted on the substrate by an anchor member having an upwardly extending end wall and wherein the proximal end of the Joule heated cantilever and proximal end of the non-heated cantilever are fastened to the anchor member. It will be appreciated however, that the bend actuator may be positioned internally or externally of the nozzle chamber. Similarly, the actuator may be a thermal bend actuator or activate in some other manner such as piezo-electric means and it follows that it does not need to be a two armed cantilever. Indeed, in some forms of the invention, the bend actuator need not be in the form of a cantilever at all.
Preferably, the anchor member is provided with side portions extending totally from the ends of the end wall so that the anchor member is substantially U-shaped when viewed from above the substrate.
Preferably, the U-shaped anchor member is positioned to wrap around the proximal end of the bend actuator with the side portions of the anchor member lying alongside the bend actuator.
Preferably, the side portions of the anchor member are provided with recesses, and one of the Joule heated cantilever and the non-heated cantilever is provided with outwardly extending portions engagable in said recesses.
Preferably, the Joule heated cantilever is mounted above the non-heated cantilever.
According to a further form of the invention, there is provided a thermal bend actuator manufactured by MEMS techniques and mounted by way of an anchor above a substrate, the bend actuator being configured to bend toward the substrate when actuated, the bend actuator comprising a Joule heated cantilever positioned above and restrained by a non-heated cantilever, the two cantilevers being joined together at their distal ends, whereby the bending of the actuator towards the substrate is caused by expansion of the Joule heated cantilever constrained by the non-heated cantilever.
Preferably, the proximal end of the Joule heated cantilever and proximal end of non-heated cantilever are independently connected to a U-shaped anchor member, in turn mounted on the substrate.